pH was monitored daily via the system computer and weekly by manual measurement of the experimental aquaria using a Metrohm 826 pH mobile electrode, calibrated with NIST J Metrohm AG is a leading provider of instruments and knowhow for chemical analysis in the lab and in the process, specializing in titration, ion chromatography, electrochemistry, and spectroscopy. The following instruments, accessories and solutions are required for carrying out the ph calibration and measurement described below: 826 ph mobile ( XX0) or 827 ph lab ( X, X) ph electrode 4.